US20050238938A1 - Membranes for fuel cells - Google Patents
Membranes for fuel cells Download PDFInfo
- Publication number
- US20050238938A1 US20050238938A1 US10/527,043 US52704305A US2005238938A1 US 20050238938 A1 US20050238938 A1 US 20050238938A1 US 52704305 A US52704305 A US 52704305A US 2005238938 A1 US2005238938 A1 US 2005238938A1
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- United States
- Prior art keywords
- fuel cell
- ixr
- direct methanol
- methanol fuel
- membrane
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- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- 239000012528 membrane Substances 0.000 title claims abstract description 73
- 239000000446 fuel Substances 0.000 title claims abstract description 69
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims abstract description 198
- 239000003054 catalyst Substances 0.000 claims abstract description 37
- 238000005342 ion exchange Methods 0.000 claims abstract description 25
- 239000007787 solid Substances 0.000 claims abstract description 17
- 239000005518 polymer electrolyte Substances 0.000 claims abstract description 16
- 229920002313 fluoropolymer Polymers 0.000 claims abstract description 12
- 229920000642 polymer Polymers 0.000 claims description 56
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical group [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 8
- 125000004432 carbon atom Chemical group C* 0.000 claims description 5
- 150000003839 salts Chemical class 0.000 claims description 4
- 229910052783 alkali metal Inorganic materials 0.000 claims description 3
- 150000001340 alkali metals Chemical class 0.000 claims description 3
- 125000000217 alkyl group Chemical group 0.000 claims description 2
- 229910052731 fluorine Inorganic materials 0.000 claims description 2
- 239000000243 solution Substances 0.000 description 17
- 229920000557 Nafion® Polymers 0.000 description 12
- 239000007789 gas Substances 0.000 description 12
- -1 hydrogen ions Chemical class 0.000 description 11
- 239000000178 monomer Substances 0.000 description 11
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 10
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 9
- 239000002253 acid Substances 0.000 description 9
- 238000000034 method Methods 0.000 description 9
- 238000000576 coating method Methods 0.000 description 8
- 239000001257 hydrogen Substances 0.000 description 8
- 229910052739 hydrogen Inorganic materials 0.000 description 8
- 238000012360 testing method Methods 0.000 description 8
- 239000011248 coating agent Substances 0.000 description 7
- BDHFUVZGWQCTTF-UHFFFAOYSA-M sulfonate Chemical compound [O-]S(=O)=O BDHFUVZGWQCTTF-UHFFFAOYSA-M 0.000 description 7
- OBTWBSRJZRCYQV-UHFFFAOYSA-N sulfuryl difluoride Chemical compound FS(F)(=O)=O OBTWBSRJZRCYQV-UHFFFAOYSA-N 0.000 description 7
- BFKJFAAPBSQJPD-UHFFFAOYSA-N tetrafluoroethene Chemical group FC(F)=C(F)F BFKJFAAPBSQJPD-UHFFFAOYSA-N 0.000 description 7
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 6
- 238000005341 cation exchange Methods 0.000 description 6
- 229920003303 ion-exchange polymer Polymers 0.000 description 6
- 230000009467 reduction Effects 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 201000000760 cerebral cavernous malformation Diseases 0.000 description 5
- 229920001577 copolymer Polymers 0.000 description 5
- 239000006185 dispersion Substances 0.000 description 5
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 5
- 239000004810 polytetrafluoroethylene Substances 0.000 description 5
- 125000000542 sulfonic acid group Chemical group 0.000 description 5
- 229910006069 SO3H Inorganic materials 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 4
- 238000009792 diffusion process Methods 0.000 description 4
- 239000003792 electrolyte Substances 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 4
- 230000007062 hydrolysis Effects 0.000 description 4
- 238000006460 hydrolysis reaction Methods 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 239000007800 oxidant agent Substances 0.000 description 4
- 230000001590 oxidative effect Effects 0.000 description 4
- QYKIQEUNHZKYBP-UHFFFAOYSA-N Vinyl ether Chemical class C=COC=C QYKIQEUNHZKYBP-UHFFFAOYSA-N 0.000 description 3
- 239000011230 binding agent Substances 0.000 description 3
- 239000008199 coating composition Substances 0.000 description 3
- 239000010411 electrocatalyst Substances 0.000 description 3
- 239000004744 fabric Substances 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 229920003223 poly(pyromellitimide-1,4-diphenyl ether) Polymers 0.000 description 3
- 239000002243 precursor Substances 0.000 description 3
- 238000002360 preparation method Methods 0.000 description 3
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 2
- 229910002848 Pt–Ru Inorganic materials 0.000 description 2
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 description 2
- 229910006095 SO2F Inorganic materials 0.000 description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 238000007334 copolymerization reaction Methods 0.000 description 2
- 229910002804 graphite Inorganic materials 0.000 description 2
- 239000010439 graphite Substances 0.000 description 2
- 239000003014 ion exchange membrane Substances 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 229910017604 nitric acid Inorganic materials 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 229910052697 platinum Inorganic materials 0.000 description 2
- 230000010287 polarization Effects 0.000 description 2
- 229920001721 polyimide Polymers 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 238000007639 printing Methods 0.000 description 2
- 239000000376 reactant Substances 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- TXEYQDLBPFQVAA-UHFFFAOYSA-N tetrafluoromethane Chemical group FC(F)(F)F TXEYQDLBPFQVAA-UHFFFAOYSA-N 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- 125000000391 vinyl group Chemical group [H]C([*])=C([H])[H] 0.000 description 2
- NWUYHJFMYQTDRP-UHFFFAOYSA-N 1,2-bis(ethenyl)benzene;1-ethenyl-2-ethylbenzene;styrene Chemical compound C=CC1=CC=CC=C1.CCC1=CC=CC=C1C=C.C=CC1=CC=CC=C1C=C NWUYHJFMYQTDRP-UHFFFAOYSA-N 0.000 description 1
- TUFKHKZLBZWCAW-UHFFFAOYSA-N 2-(1-ethenoxypropan-2-yloxy)ethanesulfonyl fluoride Chemical compound C=COCC(C)OCCS(F)(=O)=O TUFKHKZLBZWCAW-UHFFFAOYSA-N 0.000 description 1
- SVQOKUWDNBOKFD-UHFFFAOYSA-N 2-ethenoxyethanesulfonyl fluoride Chemical compound FS(=O)(=O)CCOC=C SVQOKUWDNBOKFD-UHFFFAOYSA-N 0.000 description 1
- 239000002028 Biomass Substances 0.000 description 1
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 229920006362 Teflon® Polymers 0.000 description 1
- 239000000809 air pollutant Substances 0.000 description 1
- 231100001243 air pollutant Toxicity 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 150000003863 ammonium salts Chemical class 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 238000000429 assembly Methods 0.000 description 1
- 230000000712 assembly Effects 0.000 description 1
- 125000004429 atom Chemical group 0.000 description 1
- 239000011324 bead Substances 0.000 description 1
- 238000002144 chemical decomposition reaction Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003034 coal gas Substances 0.000 description 1
- 230000002860 competitive effect Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 229920001971 elastomer Polymers 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 125000001153 fluoro group Chemical group F* 0.000 description 1
- XUCNUKMRBVNAPB-UHFFFAOYSA-N fluoroethene Chemical compound FC=C XUCNUKMRBVNAPB-UHFFFAOYSA-N 0.000 description 1
- 239000003365 glass fiber Substances 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- HCDGVLDPFQMKDK-UHFFFAOYSA-N hexafluoropropylene Chemical group FC(F)=C(F)C(F)(F)F HCDGVLDPFQMKDK-UHFFFAOYSA-N 0.000 description 1
- 229920001519 homopolymer Polymers 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 238000005470 impregnation Methods 0.000 description 1
- 239000003456 ion exchange resin Substances 0.000 description 1
- 229920000554 ionomer Polymers 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- COTNUBDHGSIOTA-UHFFFAOYSA-N meoh methanol Chemical compound OC.OC COTNUBDHGSIOTA-UHFFFAOYSA-N 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- 238000010422 painting Methods 0.000 description 1
- 230000003071 parasitic effect Effects 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 239000003495 polar organic solvent Substances 0.000 description 1
- 229920002493 poly(chlorotrifluoroethylene) Polymers 0.000 description 1
- 229920001748 polybutylene Polymers 0.000 description 1
- 239000005023 polychlorotrifluoroethylene (PCTFE) polymer Substances 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 239000002952 polymeric resin Substances 0.000 description 1
- 229920000098 polyolefin Polymers 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 229920002379 silicone rubber Polymers 0.000 description 1
- 239000004945 silicone rubber Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 238000003892 spreading Methods 0.000 description 1
- 238000000629 steam reforming Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 125000001273 sulfonato group Chemical group [O-]S(*)(=O)=O 0.000 description 1
- 150000003460 sulfonic acids Chemical class 0.000 description 1
- 125000002128 sulfonyl halide group Chemical group 0.000 description 1
- 229920003002 synthetic resin Polymers 0.000 description 1
- 239000002023 wood Substances 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/1009—Fuel cells with solid electrolytes with one of the reactants being liquid, solid or liquid-charged
- H01M8/1011—Direct alcohol fuel cells [DAFC], e.g. direct methanol fuel cells [DMFC]
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
- H01M8/1018—Polymeric electrolyte materials
- H01M8/102—Polymeric electrolyte materials characterised by the chemical structure of the main chain of the ion-conducting polymer
- H01M8/1023—Polymeric electrolyte materials characterised by the chemical structure of the main chain of the ion-conducting polymer having only carbon, e.g. polyarylenes, polystyrenes or polybutadiene-styrenes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
- H01M8/1018—Polymeric electrolyte materials
- H01M8/1039—Polymeric electrolyte materials halogenated, e.g. sulfonated polyvinylidene fluorides
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
- H01M8/1018—Polymeric electrolyte materials
- H01M8/1067—Polymeric electrolyte materials characterised by their physical properties, e.g. porosity, ionic conductivity or thickness
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/24—Grouping of fuel cells, e.g. stacking of fuel cells
- H01M8/2455—Grouping of fuel cells, e.g. stacking of fuel cells with liquid, solid or electrolyte-charged reactants
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/8605—Porous electrodes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/90—Selection of catalytic material
- H01M4/92—Metals of platinum group
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/90—Selection of catalytic material
- H01M4/92—Metals of platinum group
- H01M4/921—Alloys or mixtures with metallic elements
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/1004—Fuel cells with solid electrolytes characterised by membrane-electrode assemblies [MEA]
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
Definitions
- This invention relates to membranes and their use in electrode assemblies (MEA) for fuel cells.
- Electrochemical cells are devices that convert fuel and oxidant to electrical energy.
- Electrochemical cells generally include an anode electrode and a cathode electrode separated by an electrolyte.
- a well-known use of electrochemical cells is in a stack for a fuel cell that uses a proton exchange membrane (hereafter “PEM”) as the electrolyte.
- PEM proton exchange membrane
- a reactant or reducing fuel such as hydrogen is supplied to the anode electrode
- an oxidant such as oxygen or air is supplied to the cathode electrode.
- the hydrogen electrochemically reacts at a surface of the anode electrode to produce hydrogen ions and electrons.
- the electrons are conducted to an external load circuit and then returned to the cathode electrode, while hydrogen ions transfer through the electrolyte to the cathode electrode, where they recombine with the oxidant to produce water and release thermal energy.
- methanol fuel cell is a potentially attractive power source for vehicles and other low to medium power applications such as uninterruptible power supplies and lawn mowers, in the military as well as the commercial sectors.
- Benefits to be derived from use of methanol fuel cells as power sources include dramatic reductions in emissions of air pollutants, reduction in the nation's dependence on imported petroleum since methanol can be made from indigenous fuels such as coal and natural gas and also from renewable sources such as wood and biomass, and an overall increase in vehicle energy efficiency.
- Methanol fuel cell systems currently under development use low-temperature steam reformers in conjunction with fuel cell stacks to generate power from methanol in indirect systems.
- indirect it is meant that methanol fuel is processed (by a reformer) before it is introduced into the fuel cell stack.
- the system can be vastly simplified, and the overall system thermal efficiency can be improved if direct anodic oxidation of methanol is achieved at low polarization.
- a direct methanol fuel cell will also be preferred for vehicular applications because its weight, volume, start-up and load-following characteristics should be more attractive than the more complex indirect systems.
- DMPEMFC direct methanol PEMFC
- methanol permeates from the anode chamber of the PEMFC across the membrane, to the cathode catalyst, and reacts with reactant air (O 2 ), resulting in a parasitic loss of methanol fuel and reduced fuel cell voltage.
- Performance losses of 40-70 mV at a given current density have been observed at the cathode of PEMFCs with a direct methanol feed (Potje-Kamloth et al., Abstract No. 105, Extended Abstracts, Vol. 92-2, Fall Meeting of the Electrochemical Society, 1992).
- Power Sources 52, 77 (1994) have observed a loss of at least 100 mV for the air (O 2 ) electrode when operated in a gas-feed DMPEMFC. This translates into an approximately 10% decrease in air (O 2 ) cathode performance output as compared to a cell operating without direct methanol feed.
- DMPEMFCs must be oversized, resulting in a larger, heavier and more expensive fuel cell. To be competitive, these parameters must be minimized.
- a direct methanol fuel cell comprising:
- the invention further provides a direct methanol fuel cell, wherein the IXR is typically about 17 to about 29, and more typically 19 to about 23.
- FIG. 1 is a schematic illustration of a single cell assembly.
- FIG. 2 is a schematic illustration of a typical DMFC test station.
- FIG. 3 is a graph showing the performance of a DMFC using membranes having ion exchange ratios of 23 and 15 at an operating temperature of 28° C.
- FIG. 4 is a graph showing the performance of a DMFC using membranes having ion exchange ratios of 23 and 15 at an operating temperature of 60° C.
- a direct methanol fuel cell's efficiency is significantly improved by using an ion exchange membrane comprising perfluorinated polymers having an ion exchange ratio (IXR) of at least about 17, more typically about 17 to about 29, when compared to fuel cells wherein the membrane has the same thickness, and comprises a perfluorinated polymer having an ion exchange ratio (IXR) of at least about 15. Methanol cross-over was reduced without a reduction in power output.
- IXR perfluorinated polymers having an ion exchange ratio
- Power output is found to be equal to or increased up to 15%, typically increased by at least about 5%, and more typically increased by about 10 to 15%, at temperatures of less than 60° C.
- the methanol cross-over rate is reduced by at least about 20%; typically reduced by at least about 40%, and more typically reduced by 50 to about 75%.
- Methanol cross-over is dependant on thickness.
- the thickness of the membrane is typically about 75 ⁇ to about 250 ⁇ , more typically about 125 ⁇ to about 250 ⁇ .
- EW equivalent weight
- a reduction of about 75% in methanol cross-over may be achieved.
- a similar membrane having a thickness of about 177.8 ⁇ L a reduction of about 60% in methanol cross-over may be achieved.
- the solid fluorinated polymer electrolyte membrane having an IXR of about 17 to about 29 comprises an ion exchange polymer that is typically a highly fluorinated ion-exchange polymer.
- “Highly fluorinated” means that at least 90% of the total number of univalent atoms in the polymer are fluorine atoms. Most typically, the polymer is perfluorinated. It is also typical for use in fuel cells for the polymers to have sulfonate ion exchange groups.
- the term “sulfonate ion exchange groups” is intended to refer to either sulfonic acid groups or salts of sulfonic acid groups, typically alkali metal or ammonium salts.
- the sulfonic acid form of the polymer is typical. If the polymer in the electrocatalyst coating composition is not in sulfonic acid form when used, a post treatment acid exchange step will be required to convert the polymer to acid form prior to use.
- the ion exchange polymer employed comprises a polymer backbone with recurring side chains attached to the backbone with the side chains carrying the ion exchange groups.
- Possible polymers include homopolymers or copolymers of two or more monomers. Copolymers are typically formed from one monomer which is a nonfunctional monomer and which provides carbon atoms for the polymer backbone. A second monomer provides both carbon atoms for the polymer backbone and also contributes the side chain carrying the cation exchange group or its precursor, e.g., a sulfonyl halide group such a sulfonyl fluoride (—SO 2 F), which can be subsequently hydrolyzed to a sulfonate ion exchange group.
- a sulfonyl halide group such as a sulfonyl fluoride (—SO 2 F)
- copolymers of a first fluorinated vinyl monomer together with a second fluorinated vinyl monomer having a sulfonyl fluoride group can be used.
- Possible first monomers include tetrafluoroethylene (TFE), hexafluoropropylene, vinyl fluoride, vinylidine fluoride, trifluoroethylene, chlorotrifluoroethylene, perfluoro (alkyl vinyl ether), and mixtures thereof.
- Possible second monomers include a variety of fluorinated vinyl ethers with sulfonate ion exchange groups or precursor groups which can provide the desired side chain in the polymer.
- the first monomer may also have a side chain which does not interfere with the ion exchange function of the sulfonate ion exchange group. Additional monomers can also be incorporated into these polymers if desired.
- the typical polymers include, for example, polymers disclosed in U.S. Pat. No. 3,282,875 and in U.S. Pat. Nos. 4,358,545 and 4,940,525.
- One typical polymer comprises a perfluorocarbon backbone and the side chain is represented by the formula —O—CF 2 CF(CF 3 )—O—CF 2 CF 2 SO 3 H. Polymers of this type are disclosed in U.S. Pat. No.
- 3,282,875 and can be made by copolymerization of tetrafluoroethylene (TFE) and the perfluorinated vinyl ether CF 2 ⁇ CF—O—CF 2 CF(CF 3 )—O—CF 2 CF 2 SO 2 F, perfluoro(3,6-dioxa-4-methyl-7-octenesulfonyl fluoride) (PDMOF), followed by conversion to sulfonate groups by hydrolysis of the sulfonyl fluoride groups and ion exchanging to convert to the acid, also known as the proton form.
- TFE tetrafluoroethylene
- PMMAF perfluoro(3,6-dioxa-4-methyl-7-octenesulfonyl fluoride)
- 4,358,545 and 4,940,525 has the side chain —O—CF 2 CF 2 SO 3 H.
- This polymer can be made by copolymerization of tetrafluoroethylene (TFE) and the perfluorinated vinyl ether CF 2 ⁇ CF—O—CF 2 CF 2 SO 2 F, perfluoro(3-oxa-4-pentenesulfonyl fluoride) (POPF), followed by hydrolysis and acid exchange.
- TFE tetrafluoroethylene
- POPF perfluoro(3-oxa-4-pentenesulfonyl fluoride)
- the ion exchange capacity of a polymer can be expressed in terms of ion exchange ratio (“IXR”).
- IXR ion exchange ratio
- IXR is defined as number of carbon atoms in the polymer backbone in relation to the ion exchange groups.
- IXR can be varied as desired for the particular application.
- the ion exchange capacity of a polymer is often expressed in terms of equivalent weight (EW).
- equivalent weight (EW) is defined to be the weight of the polymer in acid form required to neutralize one equivalent of sodium hydroxide.
- the equivalent weight range which corresponds to an IXR of about 17 to about 29 is about 1200 EW to about 1800 EW.
- the polymer has an EW of 1500 corresponding to an IXR of 23.
- the equivalent weight is somewhat lower because of the lower molecular weight of the monomer unit containing a cation exchange group.
- the corresponding equivalent weight range is about 1028 EW to about 1628 EW.
- the membrane may be made of a blend of two or more polymers such as two or more highly fluorinated polymers having different ion exchange groups and/or different ion exchange capacities.
- the thickness of the membrane can be varied as desired for a particular electrochemical cell application. Typically, the thickness of the membrane is generally less than about 250 ⁇ m, preferably in the range of about 25 ⁇ m to about 150 ⁇ m. When the membrane is a monolithic high-IXR membrane, thickness is preferably no more than about 100 ⁇ m.
- the membrane may optionally include a porous support for the purposes of improving mechanical properties, for decreasing cost and/or other reasons.
- the porous support of the membrane may be made from a wide range of components.
- the porous support of the present invention may be made from a hydrocarbon such as a polyolefin, e.g., polyethylene, polypropylene, polybutylene, copolymers of those materials, and the like. Perhalogenated polymers such as polychlorotrifluoroethylene may also be used.
- the support preferably is made of a highly fluorinated polymer, most preferably perfluorinated polymer.
- Microporous PTFE films and sheeting are known which are suitable for use as a support layer.
- U.S. Pat. No. 3,664,915 discloses uniaxially stretched film having at least 40% voids.
- U.S. Pat. Nos. 3,953,566, 3,962,153 and 4,187,390 disclose porous PTFE films having at least 70% voids.
- the porous support may be a fabric made from fibers of the polymers discussed above woven using various weaves such as the plain weave, basket weave, leno weave, or others.
- a membrane can be made using the porous support by coating the ion exchange polymer, preferably the cation exchange polymer, on the support so that the coating is on the outside surfaces as well as being distributed through the internal pores of the support. This may be accomplished by impregnating the porous support solution/dispersion with the cation exchange polymer or cation exchange polymer precursor using a solvent which is not harmful to the polymer of the support under the impregnation conditions and which can form a thin, even coating of the cation exchange polymer on the support.
- a 1-10 weight percent solution/dispersion of the polymer in water mixed with sufficient amount of a polar organic solvent can be used.
- the support with the solution/dispersion is dried to form the membrane.
- reinforced membranes include the pTFE-yarn embedded type and the pTFE-fibril dispersed type dispersed uniformly in an ion-exchange resin as disclosed in 2000 Fuel Cell Seminar (Oct. 30 to Nov. 2, 2000, Portland, Oreg., USA) Abstracts p-23.
- the fuel cell comprises a catalyst coated membrane (CCM) ( 10 ) in combination with a gas diffusion backing (GDB)
- CCM catalyst coated membrane
- GDB gas diffusion backing
- CCM manufacture A variety of techniques are known for CCM manufacture which apply an electrocatalyst coating composition similar to that described above onto the solid fluorinated polymer electrolyte membrane. Some known methods include spraying, painting, patch coating and screen, decal, pad orflexographic printing.
- the MEA ( 30 ) may be prepared by thermally consolidating the gas diffusion backing (GDB) with a CCM at a temperature of under 200° C., preferably 140-160° C.
- the CCM may be made of any type known in theart.
- an MEA comprises a solid polymer electrolyte (SPE) membrane with a thin catalyst- binder layer disposed thereon.
- the catalyst may be supported (typically on carbon) or unsupported.
- a catalyst film is prepared as a decal by spreading the catalyst ink on a flat release substrate such as Kapton® polyimide film (available from the DuPont Company).
- the decal is transferred to the surface of the SPE membrane by the application of pressure and heat, followed by removal of the release substrate to form a catalyst coated membrane (CCM) with a catalyst layer having a controlled thickness and catalyst distribution.
- CCM catalyst coated membrane
- the catalyst layer is applied directly to the membrane, such as by printing, and then the catalyst film is dried at a temperature not greater than 200° C.
- the CCM thus formed, is then combined with a GDB to form the MEA of the present invention.
- the MEA is formed, by layering the CCM and the GDB, followed by consolidating the entire structure in a single step by heating to a temperature no greater than 200° C., preferably in the range of 140-160° C., and applying pressure. Both sides of the MEA can be formed in the same manner and simultaneously. Also, the composition of the catalyst layer and GDB could be different on opposite sides of the membrane.
- the cathode catalyst dispersion was prepared in a Eiger® bead mill, manufactured by Eiger Machinery Inc., Grayslake, Ill. 60030, containing 80 ml 1.0-1.25 micron zirconia grinding media. 105 grams Platinum black catalyst powder (obtained from Colonial Metals, Elkton, Md.) and 336 grams of 3.5 wt % Nafion® solution (the polymer resin used in such a solution was typically of 930EW polymer and was in the sulfonyl fluoride form) were mixed and charged into the mill and dispersed for 2 hours. Material was withdrawn from the mill and particle size was measured.
- the ink was tested to ensure that the particle size was under 1-2 micron and the % solids in the range of 26%.
- the catalyst decal was prepared by drawing down the catalyst ink to a dimension of 5 cm ⁇ 5 cm (to give a total area of 25 cm 2 ) on a 10 cm ⁇ 10 cm piece of 3 mil thick kapton® polyimide film manufactured by E.I. duPont de Nemours & Co., Wilmington, Del. A wet coating thickness of 5 mil (125 microns) typically resulted in a catalyst loading of 4 to 5 mg Pt/cm 2 in the final CCM.
- Anode decals were prepared using a procedure similar to that described above, except that in the catalyst dispersion, the Platinum black catalyst was replaced by a 1:1 atomic ratio Platinum/Ruthenium black catalyst powder (obtained from Johnson Mathey N.J.).
- the CCM was prepared by a decal transfer method. A piece of wet Nafion® N117 membrane (4′′ ⁇ 4′′) in the H + form was used for CCM preparation. The membrane was sandwiched between two anode and cathode catalyst coated decals. Care was taken to ensure that the coatings on the two decals were registered with each other and were positioned facing the membrane.
- the entire assembly was introduced between two pre-heated (to 145 C) 8′′ ⁇ 8′′ plates of a hydraulic press and the plates of the press were brought together without wasting much time until a pressure of 5000 lbs was reached.
- the sandwich assembly was kept under pressure for ⁇ 2 mins and then the press in cooled for ⁇ 2 mins (viz., till it reached a temperature of ⁇ 60° C.) under same pressure. Then the assembly was removed from the press and the Kapton® films were slowly peeled off from the top of the membrane showing that the catalyst coating had been transferred to the membrane.
- the CCM was immersed in a tray of water (to ensure that the membrane was completely wet) and carefully transferred to a zipper bag for storage and future use.
- the CCMs were chemically treated in order to convert the ionomer in the catalyst layer from the —SO 2 F form to the proton —SO 3 H form. This requires a hydrolysis treatment followed by an acid exchange procedure.
- the hydrolysis of the CCMs was carried out in a 20 wt % NaOH solution at 80° C. for 30 min.
- the CCM's were placed between Teflon® mesh, manufactured by DuPont, and placed in the solution. The solution was stirred to assure uniform hydrolyses. After 30 minutes in the bath, the CCM's were removed and rinsed completely with fresh Dl water to remove all the NaOH.
- the CCMs were then rinsed in flowing Dl water for 15 minutes at room temperature to ensure removal of all the residual acid and finally in a water bath at 65° C. for 30 minutes. They were then packaged wet and labeled.
- the CCM ( 10 ) comprised a Nafion® perfluorinated ion exchange membrane ( 11 ); and electrodes ( 12 ), prepared from a platinum/ruthenium black catalyst and Nafion® binder on the anode side, and a platinum black catalyst and Nafion® binder on the cathode side.
- a catalyst coated membrane (CCM) prepared as described above was loosely attached in a single cell hardware (purchased from Fuel Cell Technologies, Los Alamos, N. Mex.) with ELATTM carbon cloths, purchased from E-Tek, Natick, Mass. on Pt—Ru black electrode side (microporous layer coated on single side and facing the catalyst layer) and Pt black electrode side (microporous layer coated on double side and thick layer facing the catalyst layer).
- the active area of the single cell hardware was 25 cm 2 .
- the cell assembly was attached to the fuel cell test equipment.
- FIG. 1 schematically illustrates a single cell assembly. Fuel cell test measurements were made employing a single cell test assembly obtained from Fuel Cell Technologies Inc, New Mexico.
- the MEA ( 30 ) comprised the CCM ( 10 ) sandwiched between two sheets of the GDB ( 13 ) (taking care to ensure that the GDB covered the catalyst coated area on the CCM).
- the anode and cathode gas diffusion backings ( 13 ) were ELAT gas diffusion backings with microporous layer coated single side in the case of anode GDB and double side microporous layer coated for cathode side which is purchased from E-Tek Inc., Natick, Mass. The microporous layer was disposed toward the catalyst side.
- a glass fiber reinforced silicone rubber gasket ( 19 ) (Furan—Type 1007, obtained from Stockwell Rubber Company), cut to shape to cover the exposed area of the membrane of the CCM, was placed on either side of the CCM/GDB assembly (taking care to avoid overlapping of the GDB and the gasket material).
- the entire sandwich assembly was assembled between the anode and cathode flow field graphite plates ( 21 ) of a 25 cm 2 standard single cell assembly (obtained from Fuel Cell Technologies Inc., Los Alamos, N. Mex.). The test assembly shown in FIG.
- the single cell assembly was then connected to the fuel cell test station, a schematic illustration of which is shown in the FIG. 2 .
- the components in a test station include a supply of air for use as cathode gas ( 41 ); a load box to regulate the power output from the fuel cell ( 42 ); a MeOH solution tank to hold the feed anolyte solution ( 43 ); a heater to pre-heat the MeOH solution before it enters the fuel cell ( 44 ); a liquid pump to feed the anolyte solution to the fuel cell at the desired flow rate ( 45 ); a condenser to cool the anolyte exit from the cell from the cell temperature to room temperature ( 46 ) and a collection bottle to collect the spent anolyte solution ( 47 ).
- the cathode exit gas is typically fed through a gas analyzer ( 48 ) (Model VIA 510, Horiba Instruments Inc., USA Horiba,) to determine quantitatively the amount of CO 2 that is being formed at the cathode as a result of oxidation of methanol that permeated through the membrane.
- a gas analyzer 48
- Model VIA 510 Horiba Instruments Inc., USA Horiba,
- the methanol crossover or permeability of methanol through the membrane was determined by measuring the CO 2 that exited the cathode vent with the help of an infrared ( 1 R) gas analyzer. Methanol transported across the membrane was completely oxidized to CO 2 in the presence of O 2 at the cathode. A Non-Dispersive Infrared Analyzer (Model VIA 510, Horiba Instruments Inc., USA) was used to measure the CO 2 quantitatively in the cathodic exit gas stream. The same equipment and experimental conditions described above were employed to determine the methanol crossover. The volume percent of CO 2 measured as above was converted into equivalent crossover current densities. 7 and 10 mil thick membranes as shown in Table 1 were chosen for this study.
- a catalyst coated membrane (CCM) prepared as described above was loosely attached in a single cell hardware (purchased from Fuel Cell Technologies, Los Alamos, N. Mex.) with a plain Zoltek carbon cloth (purchased from Zoltek Corporation, St Louis, Mo.) facing Pt—Ru black electrode side and ELATTM carbon cloth, purchased from E-Tek, Natick, Mass. (microporous layer coated on single side and facing the catalyst layer) on Pt black electrode side.
Abstract
The invention provides a direct methanol fuel cell comprising: (a) a solid fluorinated polymer electrolyte membrane having an ion exchange ratio (IXR) of at least about 17, wherein the solid polymer electrolyte membrane has a first surface and a second surface; and (b) at least one catalyst layer present on each of the first and second surfaces of the solid polymer electrolyte membrane; wherein the fuel cell is operated at a temperature of less than 60° C.; and wherein the methanol cross-over rate is reduced by at least about 20%; and the power output is equal to or increased up to about 15%, versus a fuel cell comprising a solid fluorinated polymer electrolyte membrane having the same thickness, and an ion exchange ratio (IXR) of about 15.
Description
- This invention relates to membranes and their use in electrode assemblies (MEA) for fuel cells.
- Fuel cells are devices that convert fuel and oxidant to electrical energy. Electrochemical cells generally include an anode electrode and a cathode electrode separated by an electrolyte. A well-known use of electrochemical cells is in a stack for a fuel cell that uses a proton exchange membrane (hereafter “PEM”) as the electrolyte. In such a cell, a reactant or reducing fuel such as hydrogen is supplied to the anode electrode, and an oxidant such as oxygen or air is supplied to the cathode electrode. The hydrogen electrochemically reacts at a surface of the anode electrode to produce hydrogen ions and electrons. The electrons are conducted to an external load circuit and then returned to the cathode electrode, while hydrogen ions transfer through the electrolyte to the cathode electrode, where they recombine with the oxidant to produce water and release thermal energy.
- Most efficient fuel cells use pure hydrogen as the fuel and oxygen as the oxidant. Unfortunately, use of pure hydrogen has a number of known disadvantages, not the least of which is the relatively high cost, and storage considerations. Consequently, attempts have been made to operate fuel cells using other than pure hydrogen as the fuel.
- For example, attempts have been made to use hydrogen-rich gas mixtures obtained from steam reforming methanol as a fuel cell feed. The methanol fuel cell is a potentially attractive power source for vehicles and other low to medium power applications such as uninterruptible power supplies and lawn mowers, in the military as well as the commercial sectors. Benefits to be derived from use of methanol fuel cells as power sources include dramatic reductions in emissions of air pollutants, reduction in the nation's dependence on imported petroleum since methanol can be made from indigenous fuels such as coal and natural gas and also from renewable sources such as wood and biomass, and an overall increase in vehicle energy efficiency.
- Methanol fuel cell systems currently under development use low-temperature steam reformers in conjunction with fuel cell stacks to generate power from methanol in indirect systems. By “indirect” it is meant that methanol fuel is processed (by a reformer) before it is introduced into the fuel cell stack. However, the system can be vastly simplified, and the overall system thermal efficiency can be improved if direct anodic oxidation of methanol is achieved at low polarization. A direct methanol fuel cell will also be preferred for vehicular applications because its weight, volume, start-up and load-following characteristics should be more attractive than the more complex indirect systems.
- One drawback to direct methanol PEMFC (DMPEMFC) is that the currently available PEM electrolytes do not totally exclude methanol. Instead, methanol permeates from the anode chamber of the PEMFC across the membrane, to the cathode catalyst, and reacts with reactant air (O2), resulting in a parasitic loss of methanol fuel and reduced fuel cell voltage. Performance losses of 40-70 mV at a given current density have been observed at the cathode of PEMFCs with a direct methanol feed (Potje-Kamloth et al., Abstract No. 105, Extended Abstracts, Vol. 92-2, Fall Meeting of the Electrochemical Society, 1992). Most recently, Kuver et al. in J. Power Sources 52, 77 (1994) have observed a loss of at least 100 mV for the air (O2) electrode when operated in a gas-feed DMPEMFC. This translates into an approximately 10% decrease in air (O2) cathode performance output as compared to a cell operating without direct methanol feed. To compensate for inefficiencies due to methanol crossover, DMPEMFCs must be oversized, resulting in a larger, heavier and more expensive fuel cell. To be competitive, these parameters must be minimized.
- In accordance with the invention, there is provided a direct methanol fuel cell comprising:
-
- (a) a solid fluorinated polymer electrolyte membrane having an ion exchange ratio (IXR) of at least about 17, wherein the solid polymer electrolyte membrane has a first surface and a second surface; and
- (b) at least one catalyst layer present on each of the first and second surfaces of the solid polymer electrolyte membrane; wherein the fuel cell is operated at a temperature of less than 60° C.; and wherein the methanol cross-over rate is reduced by at least about 20%; and the power output is equal to or increased up to about 15%, versus a fuel cell comprising a solid fluorinated polymer electrolyte membrane having the same thickness, and an ion exchange ratio (IXR) of about 15. Typically, the fluorinated polymer is a perfluorinated sulfonic acid polymer sold by E. I. duPont de Nemours and Company under the tradename of Nafion®.
- In this embodiment, the invention further provides a direct methanol fuel cell, wherein the IXR is typically about 17 to about 29, and more typically 19 to about 23.
-
FIG. 1 is a schematic illustration of a single cell assembly. -
FIG. 2 is a schematic illustration of a typical DMFC test station. -
FIG. 3 is a graph showing the performance of a DMFC using membranes having ion exchange ratios of 23 and 15 at an operating temperature of 28° C. -
FIG. 4 is a graph showing the performance of a DMFC using membranes having ion exchange ratios of 23 and 15 at an operating temperature of 60° C. - It has been discovered that at operating temperatures of less than 60° C., typically less than 55° C., more typically less than 50° C., still more typically less than 40° C., and most typically between 20 and 40° C., a direct methanol fuel cell's efficiency is significantly improved by using an ion exchange membrane comprising perfluorinated polymers having an ion exchange ratio (IXR) of at least about 17, more typically about 17 to about 29, when compared to fuel cells wherein the membrane has the same thickness, and comprises a perfluorinated polymer having an ion exchange ratio (IXR) of at least about 15. Methanol cross-over was reduced without a reduction in power output. Power output is found to be equal to or increased up to 15%, typically increased by at least about 5%, and more typically increased by about 10 to 15%, at temperatures of less than 60° C. The methanol cross-over rate is reduced by at least about 20%; typically reduced by at least about 40%, and more typically reduced by 50 to about 75%. Methanol cross-over is dependant on thickness. The thickness of the membrane is typically about 75μ to about 250μ, more typically about 125μ to about 250μ. For a membrane having a thickness of about 250μ, and an IXR of 23, ie., an equivalent weight (EW) of 1500, a reduction of about 75% in methanol cross-over may be achieved. For a similar membrane having a thickness of about 177.8 μL, a reduction of about 60% in methanol cross-over may be achieved.
- Membrane:
- The solid fluorinated polymer electrolyte membrane having an IXR of about 17 to about 29 comprises an ion exchange polymer that is typically a highly fluorinated ion-exchange polymer. “Highly fluorinated” means that at least 90% of the total number of univalent atoms in the polymer are fluorine atoms. Most typically, the polymer is perfluorinated. It is also typical for use in fuel cells for the polymers to have sulfonate ion exchange groups. The term “sulfonate ion exchange groups” is intended to refer to either sulfonic acid groups or salts of sulfonic acid groups, typically alkali metal or ammonium salts. For applications where the polymer is to be used for proton exchange as in fuel cells, the sulfonic acid form of the polymer is typical. If the polymer in the electrocatalyst coating composition is not in sulfonic acid form when used, a post treatment acid exchange step will be required to convert the polymer to acid form prior to use.
- Typically, the ion exchange polymer employed comprises a polymer backbone with recurring side chains attached to the backbone with the side chains carrying the ion exchange groups. Possible polymers include homopolymers or copolymers of two or more monomers. Copolymers are typically formed from one monomer which is a nonfunctional monomer and which provides carbon atoms for the polymer backbone. A second monomer provides both carbon atoms for the polymer backbone and also contributes the side chain carrying the cation exchange group or its precursor, e.g., a sulfonyl halide group such a sulfonyl fluoride (—SO2F), which can be subsequently hydrolyzed to a sulfonate ion exchange group. For example, copolymers of a first fluorinated vinyl monomer together with a second fluorinated vinyl monomer having a sulfonyl fluoride group (—SO2F) can be used. Possible first monomers include tetrafluoroethylene (TFE), hexafluoropropylene, vinyl fluoride, vinylidine fluoride, trifluoroethylene, chlorotrifluoroethylene, perfluoro (alkyl vinyl ether), and mixtures thereof. Possible second monomers include a variety of fluorinated vinyl ethers with sulfonate ion exchange groups or precursor groups which can provide the desired side chain in the polymer. The first monomer may also have a side chain which does not interfere with the ion exchange function of the sulfonate ion exchange group. Additional monomers can also be incorporated into these polymers if desired.
- Typical polymers include a highly fluorinated, most typically a perfluodnated, carbon backbone with a side chain represented by the formula —(O—CF2CFRf)a—O—CF2CFR′fSO3Y, wherein Rf and R′f are independently selected from F, Cl or a perfluorinated alkyl group having 1 to 10 carbon atoms, a=0, 1 or 2, and Y is H, an alkali metal, or NH4. The typical polymers include, for example, polymers disclosed in U.S. Pat. No. 3,282,875 and in U.S. Pat. Nos. 4,358,545 and 4,940,525. One typical polymer comprises a perfluorocarbon backbone and the side chain is represented by the formula —O—CF2CF(CF3)—O—CF2CF2SO3H. Polymers of this type are disclosed in U.S. Pat. No. 3,282,875 and can be made by copolymerization of tetrafluoroethylene (TFE) and the perfluorinated vinyl ether CF2═CF—O—CF2CF(CF3)—O—CF2CF2SO2F, perfluoro(3,6-dioxa-4-methyl-7-octenesulfonyl fluoride) (PDMOF), followed by conversion to sulfonate groups by hydrolysis of the sulfonyl fluoride groups and ion exchanging to convert to the acid, also known as the proton form. One typical polymer of the type disclosed in U.S. Pat. Nos. 4,358,545 and 4,940,525 has the side chain —O—CF2CF2SO3H. This polymer can be made by copolymerization of tetrafluoroethylene (TFE) and the perfluorinated vinyl ether CF2═CF—O—CF2CF2SO2F, perfluoro(3-oxa-4-pentenesulfonyl fluoride) (POPF), followed by hydrolysis and acid exchange.
- For perfluorinated polymers of the type described above, the ion exchange capacity of a polymer can be expressed in terms of ion exchange ratio (“IXR”). Ion exchange ratio is defined as number of carbon atoms in the polymer backbone in relation to the ion exchange groups. A wide range of IXR values for the polymer is possible. Within the range of less than about 33, IXR can be varied as desired for the particular application. The ion exchange capacity of a polymer is often expressed in terms of equivalent weight (EW). For the purposes of this application, equivalent weight (EW) is defined to be the weight of the polymer in acid form required to neutralize one equivalent of sodium hydroxide. In the case of a sulfonate polymer where the polymer has a perfluorocarbon backbone and the side chain is —O—CF2-CF(CF3)—O—CF2-CF2-SO3H (or a salt thereof), the equivalent weight range which corresponds to an IXR of about 17 to about 29 is about 1200 EW to about 1800 EW. Typically the polymer has an EW of 1500 corresponding to an IXR of 23. IXR for this polymer can be related to equivalent weight using the formula: 50 IXR+344=EW. While the same IXR range is used for sulfonate polymers disclosed in U.S. Pat. Nos. 4,358,545 and 4,940,525, e.g., the polymer having the side chain —O—CF2CF2SO3H (or a salt thereof), the equivalent weight is somewhat lower because of the lower molecular weight of the monomer unit containing a cation exchange group. For the preferred IXR range of about 17 to about 29, the corresponding equivalent weight range is about 1028 EW to about 1628 EW. IXR for this polymer can be related to equivalent weight using the formula: 50 IXR+178=EW.
- In addition, the membrane may be made of a blend of two or more polymers such as two or more highly fluorinated polymers having different ion exchange groups and/or different ion exchange capacities.
- The thickness of the membrane can be varied as desired for a particular electrochemical cell application. Typically, the thickness of the membrane is generally less than about 250 μm, preferably in the range of about 25 μm to about 150 μm. When the membrane is a monolithic high-IXR membrane, thickness is preferably no more than about 100 μm.
- The membrane may optionally include a porous support for the purposes of improving mechanical properties, for decreasing cost and/or other reasons. The porous support of the membrane may be made from a wide range of components. The porous support of the present invention may be made from a hydrocarbon such as a polyolefin, e.g., polyethylene, polypropylene, polybutylene, copolymers of those materials, and the like. Perhalogenated polymers such as polychlorotrifluoroethylene may also be used. For resistance to thermal and chemical degradation, the support preferably is made of a highly fluorinated polymer, most preferably perfluorinated polymer.
-
-
- (m=0 to 15, n=1 to 15).
- Microporous PTFE films and sheeting are known which are suitable for use as a support layer. For example, U.S. Pat. No. 3,664,915 discloses uniaxially stretched film having at least 40% voids. U.S. Pat. Nos. 3,953,566, 3,962,153 and 4,187,390 disclose porous PTFE films having at least 70% voids.
- Alternatively, the porous support may be a fabric made from fibers of the polymers discussed above woven using various weaves such as the plain weave, basket weave, leno weave, or others.
- A membrane can be made using the porous support by coating the ion exchange polymer, preferably the cation exchange polymer, on the support so that the coating is on the outside surfaces as well as being distributed through the internal pores of the support. This may be accomplished by impregnating the porous support solution/dispersion with the cation exchange polymer or cation exchange polymer precursor using a solvent which is not harmful to the polymer of the support under the impregnation conditions and which can form a thin, even coating of the cation exchange polymer on the support. For example, for applying a coating of perfluorinated sulfonic acid polymer to a microporous PTFE support, a 1-10 weight percent solution/dispersion of the polymer in water mixed with sufficient amount of a polar organic solvent can be used. The support with the solution/dispersion is dried to form the membrane.
- Other forms of reinforced membranes include the pTFE-yarn embedded type and the pTFE-fibril dispersed type dispersed uniformly in an ion-exchange resin as disclosed in 2000 Fuel Cell Seminar (Oct. 30 to Nov. 2, 2000, Portland, Oreg., USA) Abstracts p-23.
- While the general formulae above are representative of groups of polymers they are not intented to limit the scope of the invention.
- Fuel Cell:
- As shown in
FIG. 1 , the fuel cell comprises a catalyst coated membrane (CCM) (10) in combination with a gas diffusion backing (GDB) -
- (13) to form an unconsolidated membrane electrode assembly (MEA). The catalyst coated membrane (10) comprises a ion exchange polymer membrane (11) discussed above and catalyst layers or electrodes (12) formed from a electrocatalyst coating composition
Catalyst Coated Membrane (CCM):
- (13) to form an unconsolidated membrane electrode assembly (MEA). The catalyst coated membrane (10) comprises a ion exchange polymer membrane (11) discussed above and catalyst layers or electrodes (12) formed from a electrocatalyst coating composition
- A variety of techniques are known for CCM manufacture which apply an electrocatalyst coating composition similar to that described above onto the solid fluorinated polymer electrolyte membrane. Some known methods include spraying, painting, patch coating and screen, decal, pad orflexographic printing.
- In one embodiment of the invention, the MEA (30) may be prepared by thermally consolidating the gas diffusion backing (GDB) with a CCM at a temperature of under 200° C., preferably 140-160° C. The CCM may be made of any type known in theart. In this embodiment, an MEA comprises a solid polymer electrolyte (SPE) membrane with a thin catalyst- binder layer disposed thereon. The catalyst may be supported (typically on carbon) or unsupported. In one method of preparation, a catalyst film is prepared as a decal by spreading the catalyst ink on a flat release substrate such as Kapton® polyimide film (available from the DuPont Company). After the ink dries, the decal is transferred to the surface of the SPE membrane by the application of pressure and heat, followed by removal of the release substrate to form a catalyst coated membrane (CCM) with a catalyst layer having a controlled thickness and catalyst distribution. Alternatively, the catalyst layer is applied directly to the membrane, such as by printing, and then the catalyst film is dried at a temperature not greater than 200° C.
- The CCM, thus formed, is then combined with a GDB to form the MEA of the present invention. The MEA is formed, by layering the CCM and the GDB, followed by consolidating the entire structure in a single step by heating to a temperature no greater than 200° C., preferably in the range of 140-160° C., and applying pressure. Both sides of the MEA can be formed in the same manner and simultaneously. Also, the composition of the catalyst layer and GDB could be different on opposite sides of the membrane.
- CCM Preparation Procedure:
- The cathode catalyst dispersion was prepared in a Eiger® bead mill, manufactured by Eiger Machinery Inc., Grayslake, Ill. 60030, containing 80 ml 1.0-1.25 micron zirconia grinding media. 105 grams Platinum black catalyst powder (obtained from Colonial Metals, Elkton, Md.) and 336 grams of 3.5 wt % Nafion® solution (the polymer resin used in such a solution was typically of 930EW polymer and was in the sulfonyl fluoride form) were mixed and charged into the mill and dispersed for 2 hours. Material was withdrawn from the mill and particle size was measured. The ink was tested to ensure that the particle size was under 1-2 micron and the % solids in the range of 26%. The catalyst decal was prepared by drawing down the catalyst ink to a dimension of 5 cm×5 cm (to give a total area of 25 cm2) on a 10 cm×10 cm piece of 3 mil thick kapton® polyimide film manufactured by E.I. duPont de Nemours & Co., Wilmington, Del. A wet coating thickness of 5 mil (125 microns) typically resulted in a catalyst loading of 4 to 5 mg Pt/cm2 in the final CCM. Anode decals were prepared using a procedure similar to that described above, except that in the catalyst dispersion, the Platinum black catalyst was replaced by a 1:1 atomic ratio Platinum/Ruthenium black catalyst powder (obtained from Johnson Mathey N.J.). The CCM was prepared by a decal transfer method. A piece of wet Nafion® N117 membrane (4″×4″) in the H+ form was used for CCM preparation. The membrane was sandwiched between two anode and cathode catalyst coated decals. Care was taken to ensure that the coatings on the two decals were registered with each other and were positioned facing the membrane. The entire assembly was introduced between two pre-heated (to 145 C) 8″×8″ plates of a hydraulic press and the plates of the press were brought together without wasting much time until a pressure of 5000 lbs was reached. The sandwich assembly was kept under pressure for ˜2 mins and then the press in cooled for ˜2 mins (viz., till it reached a temperature of <60° C.) under same pressure. Then the assembly was removed from the press and the Kapton® films were slowly peeled off from the top of the membrane showing that the catalyst coating had been transferred to the membrane. The CCM was immersed in a tray of water (to ensure that the membrane was completely wet) and carefully transferred to a zipper bag for storage and future use.
- Chemical Treatment of CCMs
- The CCMs were chemically treated in order to convert the ionomer in the catalyst layer from the —SO2F form to the proton —SO3H form. This requires a hydrolysis treatment followed by an acid exchange procedure. The hydrolysis of the CCMs was carried out in a 20 wt % NaOH solution at 80° C. for 30 min. The CCM's were placed between Teflon® mesh, manufactured by DuPont, and placed in the solution. The solution was stirred to assure uniform hydrolyses. After 30 minutes in the bath, the CCM's were removed and rinsed completely with fresh Dl water to remove all the NaOH.
- Acid exchange of the CCMs that were hydrolyzed in the previous step was done in 15 wt % Nitric Acid Solution at a bath temperature of 65° C. for 45 minutes. The solution was stirred to assure uniform acid exchange. This procedure was repeated in a second bath containing 15 wt % Nitric acid solution at 65° C. for another 45 minutes.
- The CCMs were then rinsed in flowing Dl water for 15 minutes at room temperature to ensure removal of all the residual acid and finally in a water bath at 65° C. for 30 minutes. They were then packaged wet and labeled. The CCM (10) comprised a Nafion® perfluorinated ion exchange membrane (11); and electrodes (12), prepared from a platinum/ruthenium black catalyst and Nafion® binder on the anode side, and a platinum black catalyst and Nafion® binder on the cathode side.
- A 7 mil Nafion® membrane having an IXR of 23 (EW of 1500), was evaluated for fuel cell performance and methanol cross-over in a cell employing a membrane electrode assembly (MEA) of the type depicted in
FIG. 1 . A catalyst coated membrane (CCM) prepared as described above was loosely attached in a single cell hardware (purchased from Fuel Cell Technologies, Los Alamos, N. Mex.) with ELAT™ carbon cloths, purchased from E-Tek, Natick, Mass. on Pt—Ru black electrode side (microporous layer coated on single side and facing the catalyst layer) and Pt black electrode side (microporous layer coated on double side and thick layer facing the catalyst layer). The active area of the single cell hardware was 25 cm2. The cell assembly was attached to the fuel cell test equipment. - Fuel cell performance was evaluated using the following procedure:
FIG. 1 schematically illustrates a single cell assembly. Fuel cell test measurements were made employing a single cell test assembly obtained from Fuel Cell Technologies Inc, New Mexico. As shown inFIG. 1 , the MEA (30) comprised the CCM (10) sandwiched between two sheets of the GDB (13) (taking care to ensure that the GDB covered the catalyst coated area on the CCM). The anode and cathode gas diffusion backings (13) were ELAT gas diffusion backings with microporous layer coated single side in the case of anode GDB and double side microporous layer coated for cathode side which is purchased from E-Tek Inc., Natick, Mass. The microporous layer was disposed toward the catalyst side. A glass fiber reinforced silicone rubber gasket (19) (Furan—Type 1007, obtained from Stockwell Rubber Company), cut to shape to cover the exposed area of the membrane of the CCM, was placed on either side of the CCM/GDB assembly (taking care to avoid overlapping of the GDB and the gasket material). The entire sandwich assembly was assembled between the anode and cathode flow field graphite plates (21) of a 25 cm2 standard single cell assembly (obtained from Fuel Cell Technologies Inc., Los Alamos, N. Mex.). The test assembly shown inFIG. 1 was also equipped with anode inlet (14), anode outlet (15), cathode gas inlet (16), cathode gas outlet (17), aluminum end blocks (18), tied together with tie rods (not shown), electrically insulating layer (20), and gold plated current collectors (22). The bolts on the outer plates (not shown) of the single cell assembly were tightened with a torque wrench to a force of 1.5 ft.lb. - The single cell assembly was then connected to the fuel cell test station, a schematic illustration of which is shown in the
FIG. 2 . The components in a test station include a supply of air for use as cathode gas (41); a load box to regulate the power output from the fuel cell (42); a MeOH solution tank to hold the feed anolyte solution (43); a heater to pre-heat the MeOH solution before it enters the fuel cell (44); a liquid pump to feed the anolyte solution to the fuel cell at the desired flow rate (45); a condenser to cool the anolyte exit from the cell from the cell temperature to room temperature (46) and a collection bottle to collect the spent anolyte solution (47). The cathode exit gas is typically fed through a gas analyzer (48) (Model VIA 510, Horiba Instruments Inc., USA Horiba,) to determine quantitatively the amount of CO2 that is being formed at the cathode as a result of oxidation of methanol that permeated through the membrane. - With the cell at room temperature, 1 M MeOH solution and air were introduced into the anode and cathode compartments respectively through inlets (14) and (16) of the cell at the rates of 5 cc/min and 500 cc/min respectively to the anode and cathode compartments. The temperature of the single cell was slowly raised till it reached 28° C. Typically, a current-voltage polarization curve was recorded. This comprised of recording the current output from the cell as the voltage was stepped down in 50 mV steps starting from the open circuit voltage (OCV) down to 0.15 V and back up to OCV. The voltage was held constant in each step for 20 seconds to allow for the current output from the cell to stabilize.
- An aqueous solution of 1 M methanol was passed over the anode side and ambient pressure air at room temperature was passed over the cathode side. The cell was heated to 28° C. The current flowing across the cell which was a measure of the fuel cell performance was measured and recorded by scanning the potential from 0 volt to 0.8 V. The cell power density (W/cm2) is another performance measure, which was calculated from the equation, Power Density=Cell current density×Cell voltage.
- As a control, a similar measurement was done using a Nafion® N117 membrane manufactured by DuPont. The data is shown in
FIG. 3 . - Methanol Cross-Over Determination:
- The methanol crossover or permeability of methanol through the membrane was determined by measuring the CO2 that exited the cathode vent with the help of an infrared (1R) gas analyzer. Methanol transported across the membrane was completely oxidized to CO2 in the presence of O2 at the cathode. A Non-Dispersive Infrared Analyzer (Model VIA 510, Horiba Instruments Inc., USA) was used to measure the CO2 quantitatively in the cathodic exit gas stream. The same equipment and experimental conditions described above were employed to determine the methanol crossover. The volume percent of CO2 measured as above was converted into equivalent crossover current densities. 7 and 10 mil thick membranes as shown in Table 1 were chosen for this study. The CO2 content for a standard Nafion® membrane (N117) was also measured as a control. The methanol crossover data for the membranes of the invention relative to Nafion® N117 are reported in Table 1.
TABLE 1 Methanol Crossover Current Density Relative Methanol Methanol Crossover Membrane Crossover (%) Reduction (%) N117 100 — (7 mil, IXR = 15) 7 mil, IXR = 23 40 60% 10 mil, IXR = 23 25 75% - Example 1 was repeated with the following exception: the cell temperature was raised to 38° C. The data are shown in Table 2.
TABLE 2 38° C. data, 10 cm2 Graphite cell hardware Cell Relative MeOH Power Density Membrane Reistance Crossover (%) (mW/cm2) Type (ohmcm2) 1M Molar 2M Molar 1M MeOH 2 MeOH N117 0.22 100 100 30 35 (7 mil, IXR = 15) 5 mil, 0.37-0.46 50 48 35 31 IXR = 23 - A 6.0 mil Nafion® membrane having an IXR=23 (EW of 1500) was evaluated for fuel cell performance and methanol cross-over in a cell employing a membrane electrode assembly (MEA) of the type depicted in
FIG. 1 . A catalyst coated membrane (CCM) prepared as described above was loosely attached in a single cell hardware (purchased from Fuel Cell Technologies, Los Alamos, N. Mex.) with a plain Zoltek carbon cloth (purchased from Zoltek Corporation, St Louis, Mo.) facing Pt—Ru black electrode side and ELAT™ carbon cloth, purchased from E-Tek, Natick, Mass. (microporous layer coated on single side and facing the catalyst layer) on Pt black electrode side. 1 M MeOH (25 cc/min) was fed in the anode side and 3000 cc/min air was fed into the cathode chamber and the cell was heated to 60° C. in the test equipment described above. The performance was recorded as detailed in the example 1, which is shown inFIG. 4 . Although the membrane (6 mil, IXR=23,1500EW) reduces the methanol crossover compared to the Nafion® N117 membrane, it delivers poor power density as a result of higher membrane resistance at 60° C.
Claims (17)
1. A direct methanol fuel cell comprising:
(a) a solid fluorinated polymer electrolyte membrane having an ion exchange ratio (IXR) of at least about 17, wherein the solid polymer electrolyte membrane has a first surface and a second surface; and
(b) at least one catalyst layer present on each of the first and second surfaces of the solid polymer electrolyte membrane; wherein the fuel cell is operated at a temperature of less than 60° C.; and wherein the methanol cross-over rate is reduced by at least about 20%; and the power output is equal to or increased up to about 15%, versus a fuel cell comprising a solid fluorinated polymer electrolyte membrane having the same thickness, and an ion exchange ratio (IXR) of about 15.
2. The direct methanol fuel cell of claim 1 wherein IXR is 17 to 29.
3. The direct methanol fuel cell of claim 2 , wherein IXR is 19 to 23.
4. The direct methanol fuel cell of claim 3 , wherein IXR is 23.
5. The direct methanol fuel cell of claim 1 , wherein the temperature is about 50 to about 55° C.
6. The direct methanol fuel cell of claim 1 , wherein the temperature is about 40 to about 50° C.
7. The direct methanol fuel cell of claim 1 , wherein the temperature is about 20 to about 40° C.
8. The direct methanol fuel cell of claim 1 , wherein the power output is increased by about 5 to about 15%.
9. The direct methanol fuel cell of claim 8 , wherein the power output is increased by about 10 to about 15%.
10. The direct methanol fuel cell of claim 1 , wherein the thickness of the membrane is 175μ, the IXR is 23, and methanol cross-over rate is reduced by 60%.
11. The direct methanol fuel cell of claim 1 , wherein the thickness of the membrane is 250μ, the IXR is 23, and methanol cross-over rate is reduced by 75%.
12. The direct methanol fuel cell of claim 1 wherein the solid fluorinated polymer electrolyte membrane is a perfluorinated polymer.
13. The direct methanol fuel cell of claim 12 wherein the perfluorinated polymer comprises a carbon backbone and at least one side chain represented by the formula —(OCF2CFRf)a—OCF2CFR′fSO3Y, wherein Rf and R′f are independently selected from F, Cl or a perfluorinated alkyl group having 1 to 10 carbon atoms, a=0, 1 or 2, and Y is H, an alkali metal, or NH4.
14. The direct methanol fuel cell of claim 12 wherein the perfluorinated polymer comprises a carbon backbone and at least one side chain represented by the formula —O—CF2CF2SO3H, or a salt thereof.
15. The direct methanol fuel cell of claim 13 wherein the polymer has an IXR of about 17 to about 29.
16. The direct methanol fuel cell of claim 14 wherein the polymer has an IXR of about 17 to about 29.
17. The direct methanol fuel cell of claim 15 wherein the polymer has an IXR of about 23.
Priority Applications (1)
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US10/527,043 US20050238938A1 (en) | 2002-09-13 | 2003-09-12 | Membranes for fuel cells |
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US41076602P | 2002-09-13 | 2002-09-13 | |
US10/527,043 US20050238938A1 (en) | 2002-09-13 | 2003-09-12 | Membranes for fuel cells |
PCT/US2003/029160 WO2004025800A2 (en) | 2002-09-13 | 2003-09-12 | Membranes for fuel cells |
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US (1) | US20050238938A1 (en) |
EP (1) | EP1537619A4 (en) |
JP (1) | JP2005539352A (en) |
KR (1) | KR20050036994A (en) |
CN (1) | CN1689187A (en) |
AU (1) | AU2003278826A1 (en) |
WO (1) | WO2004025800A2 (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20060144791A1 (en) * | 2004-12-30 | 2006-07-06 | Debe Mark K | Platinum recovery from nanostructured fuel cell catalyst |
US20060147791A1 (en) * | 2004-12-30 | 2006-07-06 | Debe Mark K | Platinum recovery from fuel cell stacks |
US9991521B2 (en) | 2012-04-23 | 2018-06-05 | Audi Ag | Method for dispersing particles in perfluorinated polymer ionomer |
Families Citing this family (2)
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EP2932550A1 (en) | 2012-12-17 | 2015-10-21 | E. I. du Pont de Nemours and Company | Flow battery having a separator membrane comprising an ionomer |
EP3493311A4 (en) * | 2016-12-29 | 2020-04-01 | Kolon Industries, Inc. | Membrane-electrode assembly, method for manufacturing same, and fuel cell comprising same |
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US5672438A (en) * | 1995-10-10 | 1997-09-30 | E. I. Du Pont De Nemours And Company | Membrane and electrode assembly employing exclusion membrane for direct methanol fuel cell |
US5981097A (en) * | 1996-12-23 | 1999-11-09 | E.I. Du Pont De Nemours And Company | Multiple layer membranes for fuel cells employing direct feed fuels |
US5989741A (en) * | 1997-06-10 | 1999-11-23 | E.I. Du Pont De Nemours And Company | Electrochemical cell system with side-by-side arrangement of cells |
US6110333A (en) * | 1997-05-02 | 2000-08-29 | E. I. Du Pont De Nemours And Company | Composite membrane with highly crystalline porous support |
US6150426A (en) * | 1996-10-15 | 2000-11-21 | E. I. Du Pont De Nemours And Company | Compositions containing particles of highly fluorinated ion exchange polymer |
US6156451A (en) * | 1994-11-10 | 2000-12-05 | E. I. Du Pont De Nemours And Company | Process for making composite ion exchange membranes |
US6294612B1 (en) * | 1998-02-02 | 2001-09-25 | E. I. Du Pont De Nemours And Company | Highly fluorinated ion exchange/nonfunctional polymer blends |
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DE69608793T2 (en) * | 1995-03-20 | 2001-02-01 | Du Pont | MEMBRANES FOR FUEL CELLS CONTAINING INORGANIC FILLERS |
US20040018410A1 (en) * | 2002-06-10 | 2004-01-29 | Hongli Dai | Additive for direct methanol fuel cells |
-
2003
- 2003-09-12 AU AU2003278826A patent/AU2003278826A1/en not_active Abandoned
- 2003-09-12 EP EP03770344A patent/EP1537619A4/en not_active Withdrawn
- 2003-09-12 JP JP2004536577A patent/JP2005539352A/en not_active Abandoned
- 2003-09-12 KR KR1020057003973A patent/KR20050036994A/en not_active Application Discontinuation
- 2003-09-12 US US10/527,043 patent/US20050238938A1/en not_active Abandoned
- 2003-09-12 WO PCT/US2003/029160 patent/WO2004025800A2/en active Application Filing
- 2003-09-12 CN CNA038218143A patent/CN1689187A/en active Pending
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US6156451A (en) * | 1994-11-10 | 2000-12-05 | E. I. Du Pont De Nemours And Company | Process for making composite ion exchange membranes |
US5672438A (en) * | 1995-10-10 | 1997-09-30 | E. I. Du Pont De Nemours And Company | Membrane and electrode assembly employing exclusion membrane for direct methanol fuel cell |
US6150426A (en) * | 1996-10-15 | 2000-11-21 | E. I. Du Pont De Nemours And Company | Compositions containing particles of highly fluorinated ion exchange polymer |
US6552093B1 (en) * | 1996-10-15 | 2003-04-22 | E. I. Du Pont De Nemours And Company | Compositions containing particles of highly fluorinated ion exchange polymer |
US5981097A (en) * | 1996-12-23 | 1999-11-09 | E.I. Du Pont De Nemours And Company | Multiple layer membranes for fuel cells employing direct feed fuels |
US6110333A (en) * | 1997-05-02 | 2000-08-29 | E. I. Du Pont De Nemours And Company | Composite membrane with highly crystalline porous support |
US5989741A (en) * | 1997-06-10 | 1999-11-23 | E.I. Du Pont De Nemours And Company | Electrochemical cell system with side-by-side arrangement of cells |
US6294612B1 (en) * | 1998-02-02 | 2001-09-25 | E. I. Du Pont De Nemours And Company | Highly fluorinated ion exchange/nonfunctional polymer blends |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
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US20060144791A1 (en) * | 2004-12-30 | 2006-07-06 | Debe Mark K | Platinum recovery from nanostructured fuel cell catalyst |
US20060147791A1 (en) * | 2004-12-30 | 2006-07-06 | Debe Mark K | Platinum recovery from fuel cell stacks |
US9991521B2 (en) | 2012-04-23 | 2018-06-05 | Audi Ag | Method for dispersing particles in perfluorinated polymer ionomer |
Also Published As
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WO2004025800A3 (en) | 2004-06-17 |
AU2003278826A8 (en) | 2004-04-30 |
EP1537619A2 (en) | 2005-06-08 |
WO2004025800A2 (en) | 2004-03-25 |
CN1689187A (en) | 2005-10-26 |
JP2005539352A (en) | 2005-12-22 |
AU2003278826A1 (en) | 2004-04-30 |
KR20050036994A (en) | 2005-04-20 |
EP1537619A4 (en) | 2009-05-27 |
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